A fuel cell system is known, particularly, in which a membrane electrode assembly (hereinafter, referred to as MEA) generates electricity from hydrogen induced to an anode side of a fuel cell and oxygen induced to a cathode side thereof.
In the past, in the fuel cell system, hydrogen was supplied to a flow path formed on a separator.
However, in such a flow path structure, a hydrogen density distribution is formed from the vicinity of an introduction port through which hydrogen is introduced toward the vicinity of a discharge port through which hydrogen is discharged. The density of hydrogen supplied to an anode-side catalyst body on the MEA becomes uneven, thereby causing an output voltage to fluctuate and thus lowering the output voltage.
In order to solve the problem, a technology has been suggested in which a plurality of protrusions are formed on a separator in order to obtain a uniform hydrogen density distribution by the pattern of the plural protrusions (see JP-A-2002-117870)
Herein, the above-mentioned hydrogen density distribution represents the total hydrogen mass contained in a unit volume; the same meaning is applied to the following description.